Preparation Of Diamond Films By Intermediate Frequency Induction Assisted Microwave Plasma Chemical Vapor Deposition

Chemical vapor deposition?CVD?diamond films have been widely applied in many high technology fields due to the outstanding mechanical,thermal,acoustical,optical and electrical properties.Microwave plasma chemical vapor deposition?MPCVD?is the most promising method to prepare high quality diamond films due to their unique advantages in high crystalline,no pollution and few defects.In this thesis,an intermediate frequency induction heating assisted microwave plasma chemical vapor deposition?IH-MPCVD?equipment was constructed to prepare diamond films.A dumbbell shaped quartz tube was applied instead of the traditional straight arm type quartz tube.The substrate was heated by the intermediate frequency induction heater based on the NIRIM-MPCVD equipment.The microstructure of the films was observed by scanning electron microscope?SEM?.The thickness of the films was measured by SEM and the deposition rate was calculated by deviding deposition time.The crystalline phase and preferred orientation was examed by X-ray diffraction?XRD?.The relative content of the diamond by laser Raman spectroscopy?Id/In?and X-ray photoelectron spectroscopy???sp³??.The effects of pretreatment conditions on the nucleation density and composition of the films were clarified.The effects of deposition temperature?Tdep?,total pressure?Ptot?,ratio of CH4/H2 and ratio of CO2/H2 on the microstructure,phase composition,preferred orientation and deposition rate(R_dep)of diamond films have been investigated.The nucleation density on Si substrate was improved by the ultrasonic treatment of diamond powder 30-40?m in particle size for 60 min.The highest nucleation density were 10¹⁰ cm^-2 and the relative content of diamond?I_d/I_n?reached the maximum.The diamond film prepared at T_dep=600-800 ^oC were?111?-oriented.With the increase of T_dep,the grains became denser.At T_dep=750 ^oC,the relative content?I_d/I_n=1.6,??sp³?=0.57?and deposition rate(R_dep=1.7?m h^-1)of diamond films reached the maximum.The diamond film prepared at P_tot=500-5000 Pa were?111?-oriented.With the decrease of Ptot,the surface density of the films increased.At Ptot=2000 Pa,the relative content of diamond reached the maximum?Id/In=1.48,??sp³?=0.57?.At Ptot=3000 Pa,the deposition rate reached the maximum(R_dep=1.35?m h^-1).The diamond film prepared at CH₄/H₂=0.5-2.0%were?111?-oriented.With the decrease of CH₄/H₂,the microstructure of the films became faceted more.The relative content of diamond increased with decreasing the ratio of CH₄/H₂.At CH₄/H₂=1.5%,the deposition rate reached the maximum(R_dep=1.4?m h^-1).The diamond film prepared at CO₂/H₂=0.5-2.5%were?111?-oriented.With the increase of CO₂/H₂,the grain size decreased.The relative content of diamond increased with increasing the ratio of CO2/H2.The deposition rate increased with decreasing the ratio of CO₂/H₂.